Antimatter to be transported outside a lab for first time — in a van
The volatile substance will be driven across the CERN campus in trucks to different facilities, giving scientists greater opportunities to study it
Two teams of CERN physicists are racing to perform an extraordinary feat: transporting antimatter for the first time. Antimatter — matter’s mirror image — is difficult to create and extremely short-lived, because on contact with matter it instantly annihilates. One team wants to move the antimatter so that it can be studied with greater precision, and the other will use it to probe materials in the first experiments of their kind.
“If you can do it, it opens up a huge number of opportunities,” says James Dunlop, a physicist at Brookhaven National Laboratory in Upton, New York, whose research includes observing antimatter on nanosecond scales.
Every matter particle has an antimatter counterpart: its mirror image, with an opposite charge. Physicists think that antimatter and matter were created in equal amounts during the Big Bang. But why the Universe now seems to be made overwhelmingly of ordinary matter is a mystery.
Antimatter is thought to be the most expensive substance on Earth — it would cost trillions of dollars to make a gram. CERN, Europe’s particle-physics laboratory outside Geneva, Switzerland, is the only place in the world that makes antiparticles slow enough to catch and store, and hopefully transport, without annihilating. Two projects there — PUMA (antiProton Unstable Matter Annihilation) and BASE-STEP — are aiming to transport antimatter to other labs, probably in the second half of next year.
Antimatter delivery
Each team is taking antimatter on the road for different reasons. BASE-STEP wants to move antiprotons — counterparts to protons — to a location free from experimental noise, where they can be examined in finer detail. PUMA plans to transport antiprotons to a facility in which other short-lived materials are made, and use the antimatter to probe their nuclear structures.
Each project’s maiden trip will take just a few hours, and will venture only across the CERN site. But eventually the teams hope to make longer journeys to universities around Europe, giving more labs the opportunity to experiment with antimatter. BASE-STEP aims to transport antiprotons some 700 kilometres to the Heinrich Heine University Düsseldorf, where some of its team is based.
This kind of delivery service “would democratize the use, or the study, of antimatter”, says Alexandre Obertelli, a physicist at the Technical University of Darmstadt (TU Darmstadt) in Germany, and architect of the PUMA experiment.
Trapping antiprotons
The specialized ‘traps’ needed to store the antiprotons during their journey have been years in the makingtaken years. In October, BASE-STEP conducted a dummy run, transporting regular matter in their trap on the back of a truck. On 4 December, the PUMA team plans to ship its empty trap from where it’s been built at TU Darmstadt to CERN. There, the team will insert antimatter into the contraption and start tests.
To move antimatter, physicists must suspend and cool it in magnetic ‘bottles’. These require superconducting magnets to hold antiprotons in place, so that they hover without touching the sides. A mobile power generator willpower the magnets, and a cooling system that will keep the antiprotons at a chilly 4 kelvin (−269 ºC). Liquid helium will act as a back-up coolant.
Perhaps the greatest challenge is maintaining a high vacuum to prevent antimatter meeting stray matter particles and annihilating. This must be done while creating systems to let antimatter out or to allow other materials into the trap to perform experiments. All of the kit needs to be portable and adapted to withstand the forces and vibrations of being on the road. “I certainly think this is feasible, just difficult,” says Dunlop.
No official regulations yet exist about how antimatter should be transported, says Obertelli. Author Dan Brown raised fears about the dangers of the substance in his book Angels and Demons, in which terrorists steal one-quarter of a gram from CERN for use as a bomb. Obertelli says there’s no need for worry. Even if all the antiprotons PUMA plans to carry were to annihilate at once, the energy released would be equivalent to the impact of a pencil dropped from table height, he says. “There is no bang.”
The BASE-STEP trap being loaded onto a lorry during a rehearsal for antimatter transport.Credit: CERN
Existential questions
CERN makes antimatter in its Antiproton Decelerator. A beam of protons slams into a metal target, creating a spray of fast-moving antiprotons. The decelerator uses magnets, electric fields and other cooling methods to slow these antiprotons. Each of six experiments based at the facility then slows and traps the particles. Although other labs around the world create antimatter — for example, during particle collisions — CERN is the only place making a usable source of the particles to store and study in detail.
The BASE collaboration, of which BASE-STEP is a part, is one of several groups studying antimatter at CERN. The team is measuring the properties of single particles of antimatter and comparing them with those of matter. It is hunting for differences that could explain puzzles such as why the two types of matter were not created equally — which would have wiped out everything straight after the Big Bang.
“We are trying to understand why we exist,” says Barbara Maria Latacz, a BASE-STEP member based at CERN. The experiments effectively sit inside a big accelerator, which creates a background noise of stray magnetic fields. By taking the antiprotons to a quiet location, the team hopes to improve the precision of their measurements. “It will be a game-changer,” says Latacz.
BASE-STEP’s trap will contain around 1,000 antiprotons.Credit: CERN
BASE-STEP will study only a few particles, so plans to transport around 1,000 antiprotons in a one-tonne experimental set-up. But PUMA needs more like one billion antiprotons. Its researchers want to transport antiprotons to CERN’s ISOLDE facility, where they can study rare nuclei that decay too quickly to be transported.
Nuclear insights
By injecting these nuclei into the PUMA trap, the team will be able to observe antiprotons annihilating with protons and neutrons. This will give scientists unique insights into the structure of the nuclei. In particular, it could provide information about the ‘skin’ of neutrons that forms in some isotopes. “This is the only probe which is really sensitive” to this region, says Obertelli. “It’s very difficult to measure.”
PUMA’s greater number of antiprotons, and the equipment needed for injecting isotopes and detecting the annihilations, mean that it requires a much bigger trap system than BASE-STEP does, amounting to 10 tonnes of kit. The heavy truck will have to take a winding, 1.5-kilometre route to ISOLDE, says Obertelli — because the direct route involves a sharp turn and a bridge that is too weak to support the vehicle’s mass.
Both teams must integrate several technologies into a single experiment while “pushing them to their limit”, says Ina Carli, an experimental physicist at the TRIUMF particle-physics centre in Vancouver, Canada, who studies antihydrogen as part of the ALPHA experiment at CERN. Even a small failure en route could mean losing the antiprotons, and it would take weeks to prepare another attempt, she says.
“I always thought that antiproton transport was still many years away,” says Carli. “I’m really excited and keeping my fingers crossed.”
doi: https://doi.org/10.1038/d41586-024-03841-0
This story originally appeared on: Nature - Author:Elizabeth Gibney
